These guys may be squishy, but they're not to be messed with. The Cnidaria ("stinging creature") are hydras, jellyfish, sea anemones, and coral. (These words look scary, but the C's are silent). There are two phyla in the radiata branch: Cnidaria and Ctenophora. All other eumetazoa are triploblastic ("tripl" – triple and "blast" – budding). In the radiata, only two germ layers form, meaning that the embryo is diploblastic. During gastrulation, an embryo begins to form germ layers that will become the different tissues of the adult body. While we wouldn't call a jellyfish quick, they can-unlike sponges-move a little under their own power.īesides the radial body plan, the radiata differ from the rest of the eumetazoa in how the embryo develops. Nerves conduct signals quickly and allow for fast responses and complex behavior. Image from here.Įumetazoa have simple muscles and nerves that enable animals to move. The two phyla with the radial body plan like a pumpkin are called the radiata, and they make up one branch of the eumetazoa. A human head has a clearly defined left, right, back, and front. If you think about the shape of a pumpkin, there's a top and a bottom, but no left, right, back, or front. Like the difference between a pumpkin and a human head. Eumetazoans have tissues that develop from the germ layers of the embryo, and there are two basic body styles that are defined by our symmetry, either radial or bilateral. This is the beginning of the rest of the animal kingdom, the eumetazoa, or "true animals" (we eumetazoans are a little biased). Polyps and Medusas Muscles and Nervous Systems and Organs, Oh My
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